diff --git a/docker/backend/Dockerfile b/docker/backend/Dockerfile
index 2c4f9e39c..a8b3f29ed 100644
--- a/docker/backend/Dockerfile
+++ b/docker/backend/Dockerfile
@@ -26,7 +26,7 @@ RUN --mount=type=cache,target=/var/cache/apt,sharing=locked \
 apt-get -y update && apt-get -y install texlive-latex-recommended texlive-luatex texlive-plain-generic texlive-lang-german texlive-lang-english
 
 ENV PROJECT_DIR=/fradrive
-RUN mkdir -m 777 -p "${PROJECT_DIR}"
+RUN mkdir -m 7777 -p "${PROJECT_DIR}"
 WORKDIR ${PROJECT_DIR}
 ENV HOME=${PROJECT_DIR}
 ENV STACK_ROOT="${PROJECT_DIR}/.stack"